TiddlyWiki5/editions/tw5.com/tiddlers/widgets/SetWidget.tid

caption: set
created: 20131115182700000
modified: 20170712153850528
tags: Widgets
title: SetWidget
type: text/vnd.tiddlywiki

! Introduction

The set variable widget assigns a value to a specified [[variable|Variables]]. The new value of the variable is available to the content within the set variable widget.

! Content and Attributes

The content of the `<$set>` widget is the scope for the value assigned to the variable.

|!Attribute |!Description |
|name |The name of the variable to assign (defaults to "currentTiddler") |
|value |The value to assign to the variable if the filter is missing or not empty |
|tiddler |<<.from-version "5.1.15">> Optional title of the tiddler from which to read the value |
|field |<<.from-version "5.1.15">> Optional field of the tiddler from which to read the value (only used if ''tiddler'' is used) |
|index |<<.from-version "5.1.15">> Optional index of the tiddler from which to read the value (only used if ''tiddler'' is used) |
|filter |An optional filter to be evaluated and assigned to the variable (see below) |
|select |<<.from-version "5.1.14">> An optional zero-based index of the item to return from the filter output (see below) |
|emptyValue |The value to assign to the variable if the specified value is missing or empty (see below) |

!! Simple Variable Assignment

The simplest way of using set variable widget assigns a string to a variable. The following example assigns a literal string

```
<$set name="myVariable" value="Some text">
<$text text=<<myVariable>>/>
</$set>
```

Both the name and value attributes can be transcluded. For example:

```
<$set name=<<anotherVariable>> value={{template!!text}}>
<$text text=<<myVariable>>/>
</$set>
```

!! Conditional Variable Assignment

This form of the set variable widget chooses one of two specified values according to whether a filter evaluates to an empty list. Here's an example that sets a variable according to whether the current tiddler is called "myMagicTitle":

```
<$set name="myVariable" filter="[all[current]field:title[myMagicTitle]]" value="It's magic" emptyValue="It's not magic">
<$text text=<<myVariable>>/>
</$set>
```

!! Filtered List Variable Assignment

This form of the set variable widget evaluates the filter and assigns the result to the variable as a space-separated list (using double square brackets for titles containing spaces).

```
<$set name="myVariable" filter="[tag[HelloThere]]">
<$text text=<<myVariable>>/>
</$set>
```

!! Filtered Item Variable Assignment

<<.from-version "5.1.14">> This form of the set variable widget evaluates the filter and assigns the specified result to the variable as a single item (ie, not using double square brackets for titles containing spaces).

```
<$set name="myVariable" filter="[tag[HelloThere]]" select="0">
<$text text=<<myVariable>>/>
</$set>
```

!! Transcluded Variable Assignment

<<.from-version "5.1.15">> This form of the set variable widget obtains the value to assign to the variable from a value in a tiddler field or index. For example:

```
<$set name="myVariable" tiddler="HelloThere" field="text">
<$text text=<<myVariable>>/>
</$set>
```

The example above could also be written as `<$set name="myVariable" value={{HelloThere!!text}}>`. The advantage of using the ''tiddler'' attribute is that the tiddler title and field or index can themselves be computed. For example:

```
<$set name="myVariable" tiddler=<<myTiddler>> field={{$:/currentField}}>
<$text text=<<myVariable>>/>
</$set>
```